Aug. 24, 2011 -- Specialized scans can identify changes in the brains of people at risk of Alzheimer's disease, according to new research.

In the study, researchers used a special MRI scan and a special PET scan in people in their 70s and 80s who were aging normally to help identify those who had brain changes thought to be linked with Alzheimer's disease.

The scans looked for amyloid-beta plaques, one of the early changes linked with the disease, and for biochemical changes, says researcher Kejal Kantarci, MD, associate professor of radiology at the Mayo Clinic in Rochester, Minn.

About a third had high levels of plaques, she found. Those who had high levels of plaques on the PET scan also tended to have the biochemical changes found on the MRI.

"We found that these biochemical changes in the brain of normally aging people were associated with worse performance on tests of mental abilities, including memory, language, and attention," she tells WebMD.

The approach is one of several under study to identify those most at risk for developing Alzheimer's disease. Others are working on blood tests, for example.

The most common form of dementia, Alzheimer's affects about 5.4 million Americans, according to the Alzheimer's Association. While doctors often use brain imaging, evaluation of behavior, psychiatric tests, and other means to diagnose the disease, none is highly accurate.

The new study was funded by the National Institutes of Health. It is published in Neurology.

Test for Alzheimer's: Study Details

Kantarci and her colleagues evaluated 311 people, all aged 70 or older, who were part of the Mayo Clinic Study of Aging. Everyone received a PET scan to look for plaque and an MRI to look for brain metabolites linked with the disease.

They also gave everyone tests of memory, language, and other skills.

Those with the high levels of plaques also tended to have high levels of the metabolites.

However, those who had high levels of the metabolites choline and creatinine had lower test scores, regardless of their level of plaques.

"Although these biochemical changes are associated with amyloid-beta deposits, they are associated with [worse] thinking skills whether or not the person has high amyloids," Kantarci tells WebMD.

She plans to follow the men and women over time for more information.

Test for Alzheimer's: Perspective

The study findings are simply a ''snapshot in time," says Heather Snyder, PhD, senior associate director of the Alzheimer's Association. She reviewed the findings but was not involved in the research.

"This study had a decent-sized population but lasted a relatively short period of time," Snyder says in an email. "Studies such as this provide some valuable insights and generate additional research questions, but long-term follow-up is crucial."

Many people ask the Alzheimer's Association about the value of early detection or prediction, since there is no effective cure or prevention.

However, early detection can help people get care earlier, she says. It can help families plan for care. It can enable patients to join a clinical trial if they wish.

In an editorial accompanying the study, Jonathan M. Schott, MD, of the University College London, writes that a reliable way to predict Alzheimer's will become crucial as the population ages, especially if there are treatment advances.